Publication Date


Document Type


First Advisor

Willott, James F.

Degree Name

M.A. (Master of Arts)

Legacy Department

Department of Psychology


Deafness; Brain stem; Presbycusis


The C57BL/6 mouse was used as a model of human presbycusis. During the first 7 months of life, C57 mice demonstrate progressive sensorineural hearing loss for high frequencies 012 kHz) with little loss of sensitivity for lower frequencies. Hearing sensitivity continues to decline with age and eventually includes the lower frequencies as well. Auditory brainstem responses (ABRs) were obtained from C57 mice of both sexes, aged 1 to 16 months. Stimuli (1 ms duration, .1 ms rise-fall, 10/s rate) of two types were used: For "low-pass" (LP) stimuli, frequencies above 12 kHz were filtered from white noise; for "high-pass" (HP) stimuli, frequencies below 12 kHz were filtered. A wound clip over the vertex served as the active electrode and a bite-bar was the reference. ABR thresholds progressively increased by about 65 dB by 15 to 16 months of age for the HP stimulus but increased by only 55 dB for the LP stimulus. Latencies decreased from 1 month to 4 to 5 months of age, then increased to 15 to 16 months. Although this effect was more pronounced for later waves and for HP stimulation, the differences were not significant. There was a trend for latency-intensity functions to become steeper with age. Ratios of amplitudes of later ABR waves to an early wave increased with age for 80 dB stimuli. Amplitude-intensity function slopes of Waves IV and V increased with age and were moderately increased for Waves II and III, while slopes for Wave I did not change. Both amplitude effects were more pronounced for HP stimuli. Sex differences were not observed in any of these findings.


Bibliography: pages 36-49.


xii, 131 pages




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